TSB's

Certain 2004-2014 GM vehicles may be equipped with a new style of catalytic converter, technically known as the close-coupled catalytic converter, which provides quick warmup, resulting in lower tail pipe emissions earlier in the operating cycle.

If an engine breakdown or non-function occurs (such as a broken intake or exhaust valve or piston), debris may be deposited in the converter through the engine exhaust ports. If the engine is non-functioning due to a severe overheat event, damage to the ceramic “brick” in the converter may occur. This may result in ceramic debris being drawn into the engine through the cylinder head exhaust ports.

According to GM, if a replacement engine is installed, the replacement engine may fail due to the debris being introduced into the combustion chambers when the engine is started.

When replacing an engine for a breakdown or non-function, an inspection of the catalytic converter and all transferred components (such as exhaust/intake manifolds) should be performed. Any debris found must be removed. In cases of engine failure due to severe overheat, technicians should also inspect each converter for signs of melting or cracking of the ceramic brick, in which case the converter must be replaced.